One theme that we at Science-Based Medicine keep revisiting again and again is not so much a question of the science behind medical therapies (although we do discuss that issue arguably more than any other) but rather a question of why. Why is it that so many people cling so tenaciously to pseudoscience, quackery, and, frequently, conspiracy theories used by believers to justify why various pseudoscience and quackery are rejected by mainstream science and medicine? Certainly, I’ve touched on this issue before on several occasions, for example, with respect to the anti-vaccine movement, the claim that abortion causes breast cancer, and how we as humans crave certainty.

It turns out that science and science-based medicine are hard for humans to accept because they often conflict with what our senses perceive and brains interpret as irrefutable evidence. The pattern-seeking function of our brain, when evaluating questions of causation in medicine, frequently betrays us. For instance, when a parent sees her child regress into autism sometime not long after being vaccinated, the easiest, most instinctive, and most emotionally compelling conclusion is that the vaccine must have had something to do with it. When scientists tell her that, no, in large studies looking at hundreds of thousands of children, there is no good evidence that vaccination confers an increased risk of autism and a lot of evidence that it does not, it’s a very hard message to believe, because it goes against how the parent interprets what she’s seen with her own eyes. Indeed, how often have we seen believers in the vaccine-autism link pour derision on the concept that when something like autistic regression happens in close temporal proximity to vaccination that the correlation does not necessarily equal causation? Similarly, believers in “alternative medicine” who experience improvement in their symptoms also pour derision on the observation, explained so well by R. Barker Bausell in Snake Oil Science, that people frequently take remedies when their symptoms are at their worst, leading them to attribute natural regression to the mean to whatever nostrum they started taking at the time.